This invention relates to the renovation of conventional internal combustion engines, and more particularly concerns the restoration of worn cylinders of small single cylinder internal combustion engines.
Conventional piston driven internal combustion engines are characterized by having one or more pistons which travel in reciprocal motion within an equal number of cylinders. As the engine experiences wear through normal usage, the cylinder walls become scored or eroded by friction and heat created by contact with the pistons. Such wear may create a cylinder which is tapered or out-of-round. In either case, compression rings carried by the piston will fail to completely contact the cylinder wall during the entire stroke of the piston's travel. This condition results in the loss of the cylinder's ability to adequately compress an ignitable mixture of gasses, and thereby renders the engine less powerful. It is common practice in engine rebuilding to re-bore each cylinder which is worn beyond certain limits to an oversize diameter and to install oversized pistons. The re-boring process requires precise alignment of a cutting tool upon the axis of each cylinder and precise cutting of metal from the cylinder wall.
Various re-boring devices are shown in the prior art. Most such re-boring devices are cumbersome and expensive, and require specialized skills for proper operation. Certain re-boring devices are disclosed in the prior art which require a minimum of two parallel cylinders in order to achieve alignment of the device on the cylinder axis and are, therefore, impractical for re-boring small one cylinder engines. Additionally, re-boring devices have been disclosed which use only the engine block's deck and cylinder for alignment. In practice, such re-boring devices are not capable of maintaining perfect alignment of the cylinder axis during the boring process. Furthermore, most re-boring devices are incapable of maintaining alignment on the cylinder axis when removed for inspection of the bore. Each time the boring device is removed and replaced, re-alignment is necessary. Moreover, most re-boring devices are mechanical cutting tool feed apparatus which are expensive to precisely manufacture with the requisite precision, and are difficult to use because of their cumbersome size. Other devices have no feed mechanism at all and are incapable of controlling accurate cutting of the cylinder walls.
It is therefore an object of the present invention to provide an engine cylinder re-boring apparatus which is small and inexpensive.
It is another object of this invention to provide an engine re-boring apparatus which may be used without specialized machine skills.
It is a further object of the present invention to provide a re-boring apparatus of the aforesaid nature capable of accurately and consistently re-boring engine cylinders on original axes, particularly in engines having one cylinder.
It is a still further object to provide an apparatus of the aforesaid nature which may be inexpensively manufactured and is economically feasible for small engine repair shops to own and operate.
It is yet another object of this invention to provide an engine cylinder re-boring apparatus which may be adapted for use with a myriad of different engines.
These objects and other objects and advantages of the invention will be apparent from the following description.